Singlespeed & Fixed Gear"I still feel that variable gears are only for people over forty-five.
Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

i'd guess he means what the difference is between the different metals, if the reasons were so obvious he wouldn't ask, they weigh less but they are stiffer, the "cro mo" ones are technically steel, i'm not sure the difference of those listed